[USRP-users] Which ports to secure with RF terminators and how to setup loopback testing.

Marcus D. Leech patchvonbraun at gmail.com
Wed Jul 22 13:02:29 EDT 2020


On 07/22/2020 05:12 AM, Pavlos Basaras via USRP-users wrote:
> Hello,
>
> i am a newbie to this so i would appreciate all help and pointers for 
> reading/understanding what i should (please excuse possibly newbie 
> questions, thanks!).
>
> I have configured 2 usrp n310 devices, following the instructions 
> from: https://kb.ettus.com/USRP_N300/N310/N320/N321_Getting_Started_Guide
> I am connected to both over all available ports eth0/sfp0/sfp1, and 
> both "usrp_find_devices" and "uhd_usrp_probe" seem to be working properly.
>
> I would like to proceed with some real testing 
> (https://kb.ettus.com/Verifying_the_Operation_of_the_USRP_Using_UHD_and_GNU_Radio).
>
> Q1: which TX ports should be secured with RF terminators? Assuming 
> that we use e.g., only RF 0, all TX ports in the remaining RF1-3 
> should be terminated, correct? As we are not currently using any other 
> port from the
> front panel (e.g., gps, ref in, trig out, pps ), should these also be 
> terminated?  What about the daughterboard ports?
>
> Q2:  the loopback configuration refers to using one usrp to test 
> TX/RX, correct?. So the setup for this testing is a single usrp, and 
> focusing on e.g., only on RF 0, by using sma-m to sma-m cable with 
> 30dB attenuator to start testing?
>
> all the best,
> Pavlos.
>
Putting terminators on unused ports is good laboratory "hygiene" but not 
strictly necessary.

Placing 30-40dB "inline" in a loopback connection (direct connect 
between RX and TX) is mandatory, to prevent possible damage to the receiver.





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